1. Field of the Invention
The present invention relates to a sound reproducing method and to an audio signal processing apparatus for use in, for example, a surround type sound reproducing system.
2. Description of the Related Art
For listening to, for example, sounds reproduced from a compact disk (CD), or for enjoying images and sounds obtained from a television program or reproduced from a video tape or a digital video disk (DVD) in a home listening room or the like, a particular sound reproducing system, e.g., a surround type sound reproducing system may be used, which is intended to enable reproduction of sounds with movie-theater or concert-hall presence.
FIG. 9 shows an example of such a surround type sound reproducing system. In this example, left and right speakers (surround speakers) 30a and 30b are provided in addition to left and right front speakers and are placed at the rear of a listener 100.
Audio signals are reproduced in an audio signal source 10, which is a reproducing unit such as a CD player. Of these signals, a left-channel audio signal AL and a right-channel audio signal AR are respectively amplified by amplifier circuits 11a and 11b, and are output from these amplifiers to the speakers 20a and 20b.
In this example, an audio signal S1a for the left rear speaker is amplified by an amplifier circuit 12a to be supplied to the left rear speaker 30a while an audio signal S1b for the right rear speaker is amplified by an amplifier circuit 12b to be supplied to the right rear speaker 30b.
Rear speaker sounds are radiated from the rear speakers 30a and 30b in addition to those from the speakers 20a and 20b, thereby enabling the listener 100 to hear the reproduced sounds with certain original-sound presence.
In ordinary sound reproducing systems using two rear speakers in this manner, the opening angle .theta. between a front-rear axis on the listener 100 and a line extending from the listener 100 to the left rear speaker 30a along a horizontal plane, and the opening angle .theta. between the front-rear axis and a line extending from the listener 100 to the right rear speaker 30b along the horizontal plane are set to about 110.degree..
This is because 110.degree. is recommended as the opening angle .theta. with respect to the Dolby Prologic system, the Dolby AC3 system, the MPEG multichannel system and so on.
With the conventional sound reproducing system using two rear surround speakers, for example, as shown in FIG. 9, a listener is liable to be clearly conscious of the existence of the rear speakers. In a situation where a listener can clearly sense that a sound is being radiated from the rear speakers, he or she has, in the ambiance of the sound field including the sound radiated from the rear speakers, a feeling of lack of spacing from the sound sources by attraction to the rear speakers. As a result, the surrounding reproduction effect is considerably reduced.